The only reason to install ADE2.0 is if you want to read books that have been protected by Adobe DRM; this includes most bough eBooks except from Amazon, and most library eBooks.
(Even then, you woul dbe better off installing ADE 1.7.2 which is less unreliable).
If you don't want to do this, uninstalling ADE should resolve your issue.
Otherwise, for each book type that is being incorrectly opened by ADE
There is something similar on Mac Finder, not sure the details.